It will be appreciated that the brakes of a towed vehicle are normally operable by controls which actuate automatically upon actuation of the brakes of the tow vehicle. Preferably, the brake controls are adjusted to decelerate the towed vehicle a little sooner than the tow vehicle so that the towed vehicle will drag somewhat and not over-run or jackknife behind the tow vehicle.
In a jackknifing situation, where a towed vehicle is effectively heading in a different direction from the tow vehicle, and dangerously applying a transverse force thereto more drastic control measures are required. A recommended procedure is to slow down the towed vehicle or trailer by actuating only the brakes of the trailer. In some cases, it is even recommended to also accelerate the tow vehicle ahead of the trailer so that the trailer can be aligned to follow directly behind. To achieve such control, towed vehicle brakes are often provided with manual override systems whereby the towed vehicle brakes may be actuated independently of the tow vehicle brakes.
Such manual override systems require a "hands-on" operation whereby release of the associated operating lever results in deactivation of the trailer brakes, thereby allowing normal operation of the vehicle to resume The magnitude of the braking force applied to the towed vehicle brakes is dependent on the relative position of the operating lever. Towed vehicle brake controls made by Kelsey Hayes Co. and Tekonsha Engineering Co. are typical of this art.
It will be appreciated that it is difficult, even for an experienced driver, to access and control the operating lever, and at the same time to accelerate and steer the tow vehicle. Where the driver is thrown from side to side, as in a jackknifing situation, or where the driver is partially disabled because of physical discomfort or a heart attack, gaining control of a swaying trailer is even more difficult and failure has disastrous consequences. Clearly, there is a need for improved brake control systems for use in emergency situations.
Another problem which arises in the electrically operated towed vehicle brake control made by Tekonsha Engineering Co., as exemplified by the apparatus described in U.S. Pat. Nos. 3,909,075 and 3,967,863, is that the towed vehicle brakes are disabled when the tow vehicle brake light circuit is inoperative. The apparatus is designed to avoid overheating of the brake control circuit, but this has the undesirable consequence that mere faults such as a blown fuse, loose connection, broken wire and the like will cause the towed vehicle brakes to fail.
An object of this invention is to provide an emergency brake control system for towed vehicles whereby the abovementioned problems associated with conventional towed vehicle brake controls are at least partially redressed.